A hydraulic coupler is a mechanical device designed specifically to connect hoses and fittings in high-pressure hydraulic systems. These devices are typically robust and constructed from non-ferrous metals such as aluminum alloys and brass. Hydraulic couplers generally fall into two broad categories — quick release types and conventional screw couplers. Although they differ in operation, both categories feature common characteristics such as close tolerances and the inclusion of additional sealing elements such as oil-resistant O-rings. Hydraulic couplers designed for use as hose fittings will also incorporate an integral nipple or crimp sleeve used to attach the coupler to the hose.
Couplers allow hoses and fittings to be joined or attached and removed quickly and with little effort. They are used as standard additions in most fluid and gas systems, including irrigation, pneumatic, and hydraulic installations. The hydraulic coupler is one such device designed specifically for use in high-pressure oil systems. The aggressive and demanding nature of these systems necessitate specific design characteristics and a hydraulic coupler will differ significantly from, for example, a garden hose.
These couplers have to handle high pressures that often surge to levels well above normal operating norms. They also have to contend with the ravages of constant exposure to high temperatures and oil degradation without failing. Hot, high-pressure oil is also highly flammable, so spark-free materials must be used in the construction of a hydraulic coupler. These issues dictate that these couplers are generally manufactured from aluminum or brass and are significantly more robust than low-pressure types.
Hydraulic couplers usually fall into one of two broad categories, namely quick-release and screw-on types. The quick-release fittings are of a two-piece, male/female clip in design with the female half of the fitting, featuring a circular row of captive ball bearings around the entrance to the fitting. The male half features a belled section that seats in a matching chamber behind the ball bearings. The balls are pushed down in their seats by a spring-loaded sleeve that holds them firmly behind the belled section of the male fitting ensuring a secure joint. When the coupling needs to be split, the sleeve is pulled back to release the pressure on the balls, thereby allowing the male fitting to be removed.
Screw-on hydraulic coupler types work in the same fashion as conventional screw-on couplers. They also consist of a male and female half similar to the quick-release variety, but lock together by mating an internal thread on the female fitting to a matching male thread on the male half. When the outer fitting is screwed down tight, a secure seal is achieved. Both types generally feature common additions such as seal-enhancing, oil-resistant O-rings, and, in the case of hose couplers, connecting nipples or crimp sleeves.